Did you make this instructable?

Take a long bolt, and put two nuts on it. Spin them up over half way. Space them out so you can get the heads of two other shorter bolts between them and tighten them down on the flats of the shorter bolt's heads.

I would simply buy a handful of hex nuts at a hardware store (say, $1.70 worth) and use regular white glue to attach them them side to side like so:xxxxxxxxxxxxxxxxxxxxOOxxxxxxxxxxxOOxxxxxxxOOOOOOxxxxOOOOOOxxxxxxxxOOxxxxxxxxxxxOOxxxxxxxxxxxOOxxxxxxxxxxxOOxxxxxxxxxxxxxxxxxxxx

Another option would be to take a strong cube magnet and stick on the heads of three short bolts and one long bolt. (If you get a large magnet, be sure to make a magnetic path between north and south poles. Otherwise you might lean over something and end up sticking.)